A New Class of Electrochemically and Thermally Stable Lithium Salts for Lithium Battery Electrolytes: II. Conductivity of Lithium Organoborates in Dimethoxyethane and Propylene Carbonate

Abstract

A conductivity study is carried out on lithium bis[1,2 benzenediolato (2-)-O,O']borate and on lithium bis[3-fluoro-1,2benzenediolato(2-)-O,O']borate in dimethoxyethane and propylene carbonate from infinite dilution to saturation in the temperature range 228 .c T (K) <308. The electron-thawing fluorine substituent produces a decrease of the association constant by a factor of about three for PC-based solutions and 5.5 for solutions in dimethoyxyethane. The increase in the maximum of conductivity by about 30% (propylene carbonate) and about 80% (dimethoxyethane), independent of temperature, reveals the effect of ion-ion interaction on the conductivity maximum, with the solvent permittivity, viscosity, and ionic radii remaining unchanged. Synthesis, analysis, and purification of lithium bis[3-fluoro-1,2-benzenediolato(2-)O,O'Jborate, which is a candidate for lithium batteries, is described.

Conductivity and Viscosity of PC-DEC and PC-EC Solutions of LiBOB

“…The most conspicuous feature emerging from these plots is the ''dome'' shape of the surfaces, as a result of peaking in both m and w. Peaking of in m is a common feature for liquid electrolytes, reflecting the process of first increasing with the number of dissociated ions as m increases and then falling as the rise in and in ion association become dominant; this has been observed for many electrolytes of lithium salts. 1,2,[5][6][7]14,15,22,[31][32][33] Peaking of in w, on the other hand, seems to be the result of the and of DEC both being much lower than those of PC and both being monotonic functions of w. As such, as w rises from zero, the change of is first dominated by the fall of of the electrolyte causing to rise and then by the fall of of the solvent which by allowing stronger ion association causes to fall. The same behavior has been observed in LiPF 6 -(PC-DEC), 1 LiBF 4 -(PC-DEC), 2 and LiPF 6 -(EC-EMC), 7 where the linear carbonates DEC and EMC have much lower and than their cyclic counterparts PC and EC, and in LiClO 4 -(PC-DME) 8 and NaClO 4 -(PC-DME), 9 where DME ͑dimethoxyethane͒ has a much lower and than PC.…”

Two unsymmetrical lithium organoborates with mixed-ligand of croconato and oxalicdiolato or benzenediolato for lithium battery electrolytes

“…This proves that an extensive charge delocalization, in their anions, caused by strongly electron withdrawing anions (e.g. C 6 …”

“…Meanwhile, LBCB was synthesized with the procedures described previously [14]. The purification procedures for propylene carbonate (PC), ethylene carbonate (EC), 1,2-dimethoxyethane (DME), ethyl methyl carbonate (EMC), were the same as given in Barthel et al's paper [6].…”

“…Barthel et al reported a new class of electrochemically and thermally stable lithium salts [4,5] with a chelatetype boron-containing anion, such as lithium bis[3-fluoro-1,2-benzenediolato(2-)-O,O]borate(FLBBB) [6]. Xu et al also reported lithium bis(oxalate)borate (LBOB) and lithium [malonato oxalato] borate (LMOB) as advanced electrolytes for Li-ion battery [7,8].…”

Conductivity of libob-based electrolyte for lithium-ion batteries

“…After achieving a maximum conductivity, an increase in salt concentration results in higher ion aggregation and higher viscosity of the solution, which reduces the free-ion number and the ionic mobility, respectively. It is a universal phenomenon for liquid electrolytes to have a maximum in conductivity at a certain salt concentration, and it has been reported for many electrolytes of lithium salts [43][44][45][46][47].…”